Voice coil-type linear motor with cooling function

ABSTRACT

A small vacuum chamber is provided which needs no load lock chamber.  
     In a voice coil type linear motor including a closed magnetic circuit formed into the θ-shape, by a pair of outer yokes ( 11 ), an inner yoke ( 12 ) and side yokes ( 13 ) and in which an armature is fixed to an inner side of the outer yoke ( 11 ), whereas permanent magnet sides are allowed to move, a coil ( 18 ) is wound around a bobbin ( 17 ), an exterior case  23  for the bobbin is constructed so as to make a coil portion watertight, and a fluid supply port and a fluid discharge port are provided either on the bobbin or on the case, whereby a cooling fluid is made to flow between the coil and the case so as to cool the coil directly.

TECHNICAL FIELD

The present invention relates to a voice coil type linear motor, andmore particularly to a cooling construction for voice coil type linearmotors which are required to realize high thrust and high efficiency andto generate less heat.

BACKGROUND ART

Conventionally, there has existed a cooling construction for a voicecoil type linear motor including a closed magnetic circuit formed intothe θ-shape, by an inner yoke provided between a pair of outer yokesmade up of magnetic materials arranged in parallel with a longitudinalcenter axis in such a manner as to be in parallel with the pair of outeryokes and side yokes provided at both end portions of the outer yokesand the inner yoke and permanent magnets provided on inner sides of theouter yokes and on outer sides of the inner yoke with polarities of thepermanent magnets which face facing surfaces of the outer yoke and theinner yoke being made opposite, wherein an armature made up of a bobbinof non-magnetic and insulating materials and a coil provided around thebobbin is provided between the permanent magnets via air gaps in such amanner as to move in an axial direction, the cooling construction beingcharacterized in that the bobbin is formed to have a cross sectionformed into the U-shape, whereby an interior of a cooler of a thinnon-magnetic material is securely joined and fixed in place within aU-shaped groove and the coil is wound around an exterior of the cooler.

For example, according to JP-A-8-214530, a voice coil type linear motorsuch as shown in FIG. 5 is disclosed in order to provide a voice coiltype linear motor which provides a good magnetic flux convergence,realizes a uniform magnetic flux flow through yokes, effects aneffective operation of armature reaction over a whole stroke and savesspace.

In FIG. 5, a field 50 is provided by a closed magnetic field formed intothe θ-shape, by outer yokes 51, an inner yoke 52 and side yokes 53 andpermanent magnets whose polarities are made opposite, and an armature 59is provided via air gaps. The permanent magnets provided on the outeryokes 51 are made up of a plurality of permanent magnets 55 a in whichpolarities of the adjacent permanent magnets are made opposite and whichhas the same width, the permanents magnets provided on the inner yoke 52are made up of a plurality of permanent magnets 55 b in which polaritiesof the adjacent permanent magnets are made opposite and which has thesame width, and those of the permanent magnets which face each other arearranged in such a manner that the polarities thereof become different.Then, the coil is made up of a series coil 58 a which divided at anequal pitch to that of the permanent magnets 55 a and in which windingdirections of the adjacent coils are made opposite, a thrust plate 58having a flange 56 bent in a direction normal to the axial direction isfixed to sides and axial end portions of a bobbin 57, and work isconnected to the flanges 56. Then, a cooler is provided in which acoolant is caused to flow through a magnetic gap between the inner yoke52 and the bobbin 57 for cooling the coil.

In addition, a voice coil type linear motor is disclosed inJP-A-2002-27724 which has a cooling construction in which non-magneticfluid cooled pipes which are formed into an integral unit by being bentin three dimensions or connected to each other in a watertight fashionare embedded in both surfaces which are defined between a coil and acover on a non-magnetic gap side in such a manner as to extend from afluid supply port to a fluid discharge port. According to the sameunexamined patent publication, by provided a voice coil type linearmotor having a construction such as shown in FIG. 6, a cooling functioncan be obtained which is free from a reduction in thrust and which canprovide a high cooling performance and a high water tightness. In FIG.6, a closed magnetic circuit is made up of an inner yoke 62, outer yokes61 and side yokes 63, permanent magnets 65 a, 65 b are disposed on outersides of the inner yoke 62 and inner sides of the outer yokes 61, and anarmature 70 in which a coil 68 is wound around a bobbin is providedbetween the permanent magnets 65 a, 65 b via magnetic gaps. Then, acover 69 which holds the armatures 70 and covers the respective yokes61, 62, 63 and fluid cooled pipes 71 which are mounted between surfaceswhich are defined by the respective yokes 61, 62, 63 and the cover 69which face each other in such a manner as to extend along an interior ofthe cover 69 are provided, and the fluid cooled pipes 71 are such as tobe formed into an integral unit by bending a pipe line reaching from afluid supply port 71A to a fluid discharge port 71B in three dimensions.

Incidentally, in the related arts, since the cooler exists on themagnetic gap side, the magnetic gap needs to formed wider, and in orderto secure the thrust, an increase in current or the number of turnsresults, posing a problem of heat loss.

In addition, since the pipes and the bobbin are interposed between thecoil making up a heat generating portion and the cooling medium,sufficient cooling effect could not be obtained.

DISCLOSURE OF THE INVENTION

The invention is made with a view to solving these problems and anobject thereof is to provide a voice coil type linear motor whichreduces the heat loss, which can obtain sufficient cooling effect, whichis free from reduction in thrust due to effective function of a magneticfield, which prevents an increase in external dimensions, and which isinexpensive.

With a view to solving the problems, according to a first aspect of theinvention, there is provided a voice coil type linear motor with acooling function including a closed magnetic circuit formed into theθ-shape, by an inner yoke provided between a pair of outer yokes made upof magnetic materials arranged in parallel with a longitudinal centeraxis in such a manner as to be in parallel with the pair of outer yokes,the outer yokes and side yokes provided at both end portions of theinner yoke; and permanent magnets provided on inner sides of the outeryokes and on outer sides of the inner yoke with polarities of thepermanent magnets which face opposite surfaces of the outer yoke and theinner yoke being made opposite to each other or with polarities of thepermanent magnets which face only the outer yokes being made oppositeeach other to thereby a field, wherein an armature made up of a bobbinof non-magnetic and insulating materials and a coil provided around thebobbin is provided between the permanent magnets via air gaps in such amanner as to move in an axial direction or in such a manner that, on thecontrary, the armature is made stationary, whereas the permanent magnetsides move, the voice coil type linear motor with a cooling functionbeing characterized in that the coil is wound around the bobbin, in thata case is constructed on an exterior of the bobbin, in that a coilportion is made watertight, and in that a fluid supply port and a fluiddischarge port are provided on the bobbin or the case, whereby a coolingfluid is caused to flow between the coil and the case so that the coilis cooled directly.

In addition, according to a second aspect of the invention, there isprovided a voice coil type linear motor with a cooling function as setforth in the first aspect of the invention, characterized in that anO-ring is mounted between the bobbin and the case so as to realizewatertightness therebetween to thereby cool the coil directly.

In addition, according to a third aspect of the invention, there isprovided a voice coil type linear motor with a cooling function as setforth in the first aspect of the invention, characterized in thatwatertighness is realized between the bobbin and the case by joining thebobbin and the case together through bonding or a combination of bondingand screw fastening to thereby cool the coil directly.

By the configurations, since the cooling fluid enters from the fluidsupply port, flows over the surface of the coil and is discharged fromthe fluid discharge port so as to cool the coil during the flow, a voicecoil type linear motor can be obtained which reduces heat loss, whichcan obtain sufficient cooling effect, which is free from reduction inthrust due to effective function of a magnetic field, which prevents anincrease in external dimensions, and which is inexpensive.

As is described heretofore, since the armature coil is wound around thebobbin, the exterior of the bobbin is covered with the case so that thecoil portion is made to be watertight, and the fluid supply port and thefluid discharge port are provided on the bobbin or the case, whereby thecooling fluid is caused to flow between the oil and the case so as tocool the coil directly, the following advantages can be provided:

-   (1) Since the cooling efficiency is high, a high-speed and    high-response motor can be provided;-   (2) Since heat is prevented from escaping to the periphery, no    thermal influence is given to other machines mounted;-   (3) Since the magnetic field functions effectively, there is no    reduction in thrust;-   (4) The external dimensions are hardly increased; and-   (5) Production is effected inexpensively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cut-away perspective view showing the entirety ofa first embodiment of the invention.

FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1.

FIG. 3 is a sectional view taken along the line B-B in FIG. 1.

FIG. 4 is an exploded perspective view of a constituent part made up ofa bobbin, a coil and a case which is a constituent part which constitutea core of FIG. 1.

FIG. 5 shows a voice coil type linear motor having a conventionallyknown cooling construction.

FIG. 6 shows a voice coil type linear motor having anotherconventionally known cooling construction.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be described in detail based on the drawings.

FIGS. 1 to 4 shown an embodiment of the invention, wherein FIG. 1 is apartially cut-away perspective view showing the entirety of a voice coiltype linear motor, FIG. 2 is a cross-sectional view taken along the lineA-A in FIG. 1, and FIG. 3 is a sectional view taken along the line B-Bin FIG. 1. FIG. 4 is an exploded perspective view of a constituent partmade up of a bobbin, a coil and a case.

In FIGS. 1 to 3, 10 denotes a filed, 11 denotes a pair of outer yokesformed of a flat plate-like ferromagnetic material, 12 denotes an inneryoke, 13 denotes a pair of side yokes of a flat plate-like ferromagneticmaterial, 15 denotes a permanent magnet, 17 denotes a bobbin, 18 denotesan armature coil wound around the bobbin 17, 19 denotes a cover, 23denotes an outer case of the armature coil, 21A denotes a fluid supplyport, 21B denotes a fluid discharge port, and 24 denotes a fluid line24. 20 is made up of the bobbin 17, the coil 18, the case 23 and thefluid line 24.

In the voice coil type linear motor, a pair of outer yokes 11, 11 of aflat plate-like ferromagnetic material are provided in parallel with alongitudinal center axis, and permanent magnets 15 a, 15 a are disposedinside thereof. A pair of side yokes 13, 13 of a flat plate-likeferromagnetic material are fixed to both sides of the outer yokes 11, 11in such a manner as to face each other. An inner yoke 12 is fixed tocentral portions of the side yokes 13, 13. In addition, permanentmagnets 15 b, 15 b, which are magnetized to have a different polarityrelative to the permanent magnets 15 a, 15 a, are disposed on upper andlower surfaces of the inner yoke 12 in such a manner that 15 a and 15 bface each other. Namely, the outer yokes 11, 11, the side yokes 13, 13,and the inner yoke 12 forms the θ-shape, and the permanent magnets 15 a,15 b are disposed inside the shape so formed, whereby a field 10 isformed.

The armature coil 18 wound around the bobbin 17 and an exterior case 23which covers end portions of the armature coil 18 make up an armature,and the permanent magnets 15 a and 15 b are disposed with an air gapbeing provided therebetween, whereby the armature becomes a movingelement which freely moves in the axial direction.

FIG. 4 is an exploded perspective view of a constituent part made up ofthe bobbin, the coil and the case, which makes up a core constituentpart of FIG. 1.

A cooling fluid which has entered from the fluid supply port 21A passesthrough an air gap between the armature coil 18 and the exterior case 23thereof and is then discharged from the fluid discharge port 21B. Duringthe flow, the cooling fluid takes up heat from the armature coil 18 byflowing directly over the surface of the armature coil 18 to therebycool the armature coil 18.

In addition, the bobbin 17 and the exterior case 23 are made ofnon-magnetic and high electrically resistant materials and do not affectmagnetism generated in the armature coil 18. In addition, the coolingfluid is such as to have insulating properties and causes no shortcircuit of electricity applied to the armature coil 18. Furthermore, anO ring may be mounted between the bobbin 17 and the exterior case 23 toproduce watertightness therebetween. Alternatively, the bobbin 17 andthe exterior case 23 may be secure joined together through bonding or acombination of bonding and screwing to produce watertightnesstherebetween.

INDUSTRIAL APPLICABILITY

The invention can be applied, in particular, to a field where by beingapplied to a cooling construction for a voice coil type linear motorwhich is required to realize high thrust and high efficiency and togenerate less heat, a voice coil type linear motor is produced andprovided which reduces the heat loss, which can obtain sufficientcooling effect, which is free from reduction in thrust due to effectivefunction of a magnetic field, which is small in size, and which isinexpensive.

1. A voice coil type linear motor with a cooling function comprising: aclosed magnetic circuit formed into the θ-shape, by an inner yokeprovided between a pair of outer yokes made up of magnetic materialsarranged in parallel with a longitudinal center axis in such a manner asto be in parallel with the pair of outer yokes, the outer yokes and sideyokes provided at both end portions of the inner yoke; and permanentmagnets provided on inner sides of the outer yokes and on outer sides ofthe inner yoke with polarities thereof which face opposite surfaces ofthe outer yoke and the inner yoke being made opposite to each other orwith polarities thereof which face only the outer yokes being madeopposite each other to thereby a field, wherein an armature made up of abobbin of non-magnetic and insulating materials and a coil providedaround the bobbin is provided between the permanent magnets via air gapsin such a manner as to move in an axial direction or in such a mannerthat, on the contrary, the armature is made stationary, and thepermanent magnet sides move, the coil is wound around the bobbin, a caseis constructed on an exterior of the bobbin, a coil portion is madewatertight, a fluid supply port and a fluid discharge port are providedon the bobbin or the case, and a cooling fluid is caused to flow betweenthe coil and the case so that the coil is cooled directly.
 2. The voicecoil type linear motor with a cooling function as set forth in claim 1,further comprising: an O-ring mounted between the bobbin and the case soas to realize watertightness therebetween to thereby cool the coildirectly.
 3. The voice coil type linear motor with a cooling function asset forth in claim 1, wherein watertighness is realized between thebobbin and the case by joining the bobbin and the case together throughbonding or a combination of bonding and screw fastening to thereby coolthe coil directly.